Copolyester explosive or propellant compositions

ABSTRACT

Rocket propellant and explosive compositions containing, as binders, carboxy-terminated polyester resins comprising a saturated dicarboxylic acid, a saturated diol and 2-methyl-1,2,3propanetricarboxylic acid, are disclosed.

United States Patent [72] Inventors [21] Appl. No. [22] Filed Nov. 9, 1971 The United States of America as represented by the Secretary of the Navy [45] Patented [73] Assignee [54] COPOLYESTER EXPLOSIVE OR PROPELLANT COMPOSITIONS 4 Claims, No Drawings [52] U.S.Cl 149/19, 149/22, 149/36, 149/44 [51] Int. Cl C0611 5/06 [50] Field of Search 149/19 [56] References Cited UNITED STATES PATENTS 3,182,040 5/1965 Watkins et al. 260/75 3,203,842 8/1965 Godfrey 149/19 3,431,151 3/1969 Carvalho et a1 149/19 Primary Examiner-Benjamin R. Padgett Assistant Examiner-E. A. Miller Attorney-Frank M. Van Reit ABSTRACT: Rocket propellant and explosive compositions containing, as binders, carboxy-terminated polyester resins comprising a saturated dicarboxylic acid, a saturated diol and Z-methyl- 1 ,2,3-propanetricarboxylic acid, are disclosed.

COPOLYlESTER EXPLOSIVE OR PROPELLANT COMPOSITIONS CROSS-REFERENCES TO RELATED APPLICATIONS This application is a division of our copending application, Ser. No. 651,100, filed June 29, 1967 and entitled PRODUCTS.

BACKGROUND OF THE INVENTION This application relates to the field of rocket propellant compositions and more particularly to binder components for said compositions. Our new binders are polyester resins which contain sufficient Z-methyl-1,2,3-propanetricarboxylic acid so as to render the polyesters curable. The polyesters are also of such viscosity so as to facilitate mixing of solids therewith.

SUMMARY DESCRIPTION OF THE INVENTION INCLUDING PREFERRED EMBODIMENTS Our novel polyester resins may be represented by recurring units of the formula wherein x is the esterification residue of a saturated dicarboxylic acid different than 2, y is the esterification residue of a saturated diol and z is the esterification residue of 2-methyl- 1,2,3-propanetricarboxylic acid, wherein the combined amount of acid is in excess of the amount of diol excluding the pendant carboxyl groups of z, the total amount of z in the polyester ranging from about 3.0 percent to about 25.0 percent, preferably from about 5.0 percent to about 15.0 percent, by weight, based on the total weight of the polyester.

The novel polyesters may be produced by reacting the saturated dicarboxylic acid, the saturated diol and the 2-methyl 1,2,3-propanetricarboxylic acid, at the concentrations mentioned above, at the reflux (boiling) temperature of the specific compound which is used as the solvent for the charge materials. We have found that any hydrocarbon solvent which will azeotrope with water may be used for this purpose. Examples of representative solvents include benzene, toluene, xylene and the like. The reaction is preferably conducted at atmospheric pressure although higher or lower pressures may be utilized if desired or necessary, provided that corresponding changes are made in the temperature to which the reaction media is heated.

The reaction should be conducted in the presence of from about 0.1-l percent, preferably 1.0-3.0 percent, by weight, based on the weight of the charge, of a strong acid. The acid functions as a catalyst and any material known for this purpose may be used. Examples include HNO H 80 HCl, H PO p-toluene-sulfonic acid and the like.

The reaction should be allowed to continue until the theoretical amount of water is driven off in order to insure the production of the highest molecular weight.

Examples of suitable saturated dicarboxylic acids include phthalic, oxalic, malonic, succinic, glutaric, sebacic, adipic, pimelic, suberic, azelaic and the like.

Suitable saturated diols which may be used include ethylene glycol, diethylene glycol, propylene glycol, dipropylene glycol, trimethylene glycol, hexamethylene glycol, tetramethylene glycol, a, a'-dihydroxy-p-xylene, pinacol, B, B'-dihydroxy-p-diethylbenzene alkane diols, i.e. 1,4-butanediol and the like.

The polyester resins of the instant invention are generally solid waxes and, as such, it is preferable to utilize them as binders in explosives, etc., in combination with a plasticizer. Any known material may be used for this purpose with such compounds as bis(2,2-dinitro-2-fluoroethyl) formal or those disclosed and claimed in pending U.S. application Ser. No. 619,120, filed Feb. 23, 1967, being exemplary.

The resultant plasticized compositions may then be crosslinked with any known cross-linking agent, preferably the trifunctional aziridines such as those disclosed in pending applications Ser. Nos. 605,146; 605,148 and 605,149, all filed Dec. 23, 1966 and Ser. No. 574,936, filed Aug. 25, 1966.

The bis( 2,2-dinitro-2-fluoroethyl) formal is a known plasticizer and may be prepared by reacting tetranitromethane with hydrogen peroxide and sodium hydroxide to give the sodium salt of trinitromethane which is converted by direct fluorination to fluorotrinitromethane. Fluorotrinitromethane, on treatment with hydrogen peroxide and sodium hydroxide, followed by fon'naldehyde then results in the production of 2,Z-dinitro-2-fluoroethanol. This alcohol is then converted to the formal by reaction with formaldehyde.

As mentioned briefly above, our novel polyesters are useful as binders in the preparation of rocket propellant compositions and explosives. For example, one can prepare a rocket propellant or explosive by incorporating a fuel such as aluminum, magnesium, boron, carbon, etc., oxidizers such as the chromates, dichromates, permanganates, nitrates, chlorates,

and perchlorates of alkali and alkaline earth metals such as sodium, potassium calcium and the like, ammonia; hydrazine; guanidine, etc. in our polyesters along with the above plasticizers.

The following examples are set forth by way of illustration only and are not to be construed as limitations on the present invention except as set forth in the appended claims. All parts and percentages are by weight unless otherwise specified.

EXAMPLE 1 To a suitable reaction vessel is charged a mixture of 16.16 parts of sebacic acid, 3.90 parts of 2-methyl-1,2,3- propanetricarboxylic acid, 9.54 parts of diethylene glycol, 0.25 part of p-toluene sulfonic acid and parts of xylene. The mixture is refluxed for 16 hours and water, codistilling off with xylene, is separated in a trap. The xylene is then distilled in vacuo to leave a carboxy-terminated polyester, a white, waxy solid, as the residue. The neutralization equivalent of the polymer is 681 (theoretical neutralization equivalent is 659).

EXAMPLE 2 Twenty-five weight percent of the polyester of example 1 and 75 weight percent of bis(2,2-dinitro-2-fluoroethyl) formal, as a solution, are charged to a suitable vessel. To 10.8 parts of the solution is added 0.21 part of hexahydro-l,3,5- tris-[N-(Z-ethyl aziridinyl)propionyl1sa-triazine. The resultant solution is blended with 12.0 parts of ammonium perchlorate and 8.0 parts of powdered aluminum. The composition is maintained at 25 C. for 24 hours and then cured at 75 C. for 4 hours in a l dram, 15 45 mm. vial. The resultant composition is a tough, resilient elastomer. The vial is placed on the compression cell of an lnstron tester and a 0.125 inch diameter stainless steel rod is lowered into the sample at a constant rate of 0.02 inches/min. A trace is automatically recorded of the resistance of the elastomer to penetration and the depth of penetration. Values quoted are the resistance in pounds/sq. in. and penetration in inches at the point where the elastomer snaps.

TABLE ll Propellant Properties Ex. Acid Alcohol Resistance Penetration 3 adipic acid ethylene 206 0.ll

glycol 4 pimelic acid ethylene 207 0.103

glycol 5 azelaic acid l.4-hutanediol 202 0.098

We claim:

1. A rocket propellant composition or explosive comprising a plasticizer, a fuel selected from the group consisting of aluminum, magnesium, boron and carbon, an oxidizer selected from the group consisting of the chromates, dichromates, permanganates, nitrates, chlorates and perchlorates of ammonia, hydrazine, guanidine. and the alkali and alkaline earth metals, a cross-linking agent and a polyester resin comprising recurring units of the formula:

wherein x is the esterification residue ofa saturated dicarboxylic acid different than z, y is the esterification residue of a saturated diol, and z is the esterification residue of Z-methyll.2,3-propanetricarboxylic acid, wherein the combined amount of acid is in excess ofthe amount of diol excluding the pendant carboxyl group of z and the total amount ofz ranges from about 3.0 to about 25.0 percent, by weight, based on the total weight of the polyester.

2. A composition according to claim 1 wherein x is sebacic acid.

3. A composition according to claim 1 wherein y is diethylene glycol.

4. A composition according to claim I wherein .r is sebacic acid and y is diethylene glycol. 

2. A composition according to claim 1 wherein x is sebacic acid.
 3. A composition according to claim 1 wherein y is diethylene glycol.
 4. A composition according to claim 1 wherein x is sebacic acid and y is diethylene glycol. 